The present invention relates to a method of measuring the temperature of the surface of a solid, such as a silicon wafer for fabricating semiconductor devices, and a temperature measuring apparatus for carrying out the method. More particularly, the present invention relates to a method and apparatus of measuring the local temperature of a minute region on the order of square micrometers in a noncontact measuring mode.
A known noncontact temperature measuring apparatus for measuring the temperature of a silicon wafer, such as disclosed in Japanese Patent Laid-open (Kokai) No. 62-299037 or 1-129966, is a so-called radiation thermometer that uses a fact that the intensity of infrared rays emitted from the silicon wafer varies according to the temperature of the silicon wafer for measuring the temperature of the silicon wafer.
Another temperature measurement as described in "IEEE 1990 Symposium on VLSI Technology", pp. 105-106 (1990), discloses the temperature measurement of a silicon wafer by using a fact that the propagating velocity of a sound wave that propagates through or along the surface of a silicon wafer is dependent on the temperature of the silicon wafer.
When the radiation thermometer is used on a film forming apparatus, such as a semiconductor sputtering apparatus or a heat treatment apparatus, measured data includes errors because the emissivity of the silicon wafer is dependent on the process condition. Since the quantity of radiated infrared rays is proportional to the area of the point of measurement, the quantity of infrared rays radiated from a minute point of measurement having an area on the order of square micrometers is very small, which is difficult to measure.
The temperature measuring method using sound waves measures the average temperature of a portion of a length through which the sound wave propagates and is unable to measure the temperature of a minute are on the order of square micrometers.